Thursday, January 26, 2012

Introduction to Search Engine Optimization


Introduction to Search Engine Optimization


Search engines are one of the primary ways that Internet users find Web sites. That's why a Web site with good search engine listings may see a dramatic increase in traffic.
Everyone wants those good listings. Unfortunately, many Web sites appear poorly in search engine rankings or may not be listed at all because they fail to consider how search engines work.
In particular, submitting to search engines  is only part of the challenge of getting good search engine positioning. It's also important to prepare a Web site through "search engine optimization."
Search engine optimization means ensuring that your Web pages are accessible to search engines and are focused in ways that help improve the chances they will be found.

This next section provides information, techniques and a good grounding in the basics of search engine optimization. By using this information where appropriate, you may tap into visitors who previously missed your site.
The guide is not a primer on ways to trick or "spam" the search engines. In fact, there are not any "search engine secrets" that will guarantee a top listing. But there are a number of small changes you can make to your site that can sometimes produce big results.
Let's go forward and first explore the two major ways search engines get their listings; then you will see how search engine optimization can especially help with crawler-based search engines.

How Search Engines Work


The term "search engine" is often used generically to describe both crawler-based search engines and human-powered directories. These two types of search engines gather their listings in radically different ways.
Crawler-Based Search Engines
Crawler-based search engines, such as Google, create their listings automatically. They "crawl" or "spider" the web, then people search through what they have found.
If you change your web pages, crawler-based search engines eventually find these changes, and that can affect how you are listed. Page titles, body copy and other elements all play a role.
Human-Powered Directories
A human-powered directory, such as the Open Directory, depends on humans for its listings. You submit a short description to the directory for your entire site, or editors write one for sites they review. A search looks for matches only in the descriptions submitted.
Changing your web pages has no effect on your listing. Things that are useful for improving a listing with a search engine have nothing to do with improving a listing in a directory. The only exception is that a good site, with good content, might be more likely to get reviewed for free than a poor site.
"Hybrid Search Engines" Or Mixed Results
In the web's early days, it used to be that a search engine either presented crawler-based results or human-powered listings. Today, it extremely common for both types of results to be presented. Usually, a hybrid search engine will favor one type of listings over another. For example, MSN Search is more likely to present human-powered listings from LookSmart. However, it does also present crawler-based results (as provided by Inktomi), especially for more obscure queries.

The Parts Of A Crawler-Based Search Engine
Crawler-based search engines have three major elements. First is the spider, also called the crawler. The spider visits a web page, reads it, and then follows links to other pages within the site. This is what it means when someone refers to a site being "spidered" or "crawled." The spider returns to the site on a regular basis, such as every month or two, to look for changes.
Everything the spider finds goes into the second part of the search engine, the index. The index, sometimes called the catalog, is like a giant book containing a copy of every web page that the spider finds. If a web page changes, then this book is updated with new information.
Sometimes it can take a while for new pages or changes that the spider finds to be added to the index. Thus, a web page may have been "spidered" but not yet "indexed." Until it is indexed -- added to the index -- it is not available to those searching with the search engine.
Search engine software is the third part of a search engine. This is the program that sifts through the millions of pages recorded in the index to find matches to a search and rank them in order of what it believes is most relevant. You can learn more about how search engine software ranks web pages on the aptly-named How Search Engines Rank Web Pages page.

Major Search Engines: The Same, But Different
All crawler-based search engines have the basic parts described above, but there are differences in how these parts are tuned. That is why the same search on different search engines often produces different results. Some of the significant differences between the major crawler-based search engines are summarized on the Search Engine Features Page. Information on this page has been drawn from the help pages of each search engine, along with knowledge gained from articles, reviews, books, independent research, tips from others and additional information received directly from the various search engines.
Now let's look more about how crawler-based search engine rank the listings that they gather.

Whenever you enter a query in a search engine and hit 'enter' you get a list of web results that contain that query term. Users normally tend to visit websites that are at the top of this list as they perceive those to be more relevant to the query. If you have ever wondered why some of these websites rank better than the others then you must know that it is because of a powerful web marketing technique called Search Engine Optimization (SEO).
SEO is a technique which helps search engines find and rank your site higher than the millions of other sites in response to a search query. SEO thus helps you get traffic from search engines.
This SEO tutorial covers all the necessary information you need to know about Search Engine Optimization - what is it, how does it work and differences in the ranking criteria of major search engines.

1. How Search Engines Work

The first basic truth you need to know to learn SEO is that search engines are not humans. While this might be obvious for everybody, the differences between how humans and search engines view web pages aren't. Unlike humans, search engines are text-driven. Although technology advances rapidly, search engines are far from intelligent creatures that can feel the beauty of a cool design or enjoy the sounds and movement in movies. Instead, search engines crawl the Web, looking at particular site items (mainly text) to get an idea what a site is about. This brief explanation is not the most precise because as we will see next, search engines perform several activities in order to deliver search results – crawlingindexingprocessingcalculating relevancy, andretrieving.
First, search engines crawl the Web to see what is there. This task is performed by a piece of software, called a crawler or a spider (or Googlebot, as is the case with Google). Spiders follow links from one page to another and index everything they find on their way. Having in mind the number of pages on the Web (over 20 billion), it is impossible for a spider to visit a site daily just to see if a new page has appeared or if an existing page has been modified, sometimes crawlers may not end up visiting your site for a month or two.
What you can do is to check what a crawler sees from your site. As already mentioned, crawlers are not humans and they do not see images, Flash movies, JavaScript, frames, password-protected pages and directories, so if you have tons of these on your site, you'd better run theSpider Simulator below to see if these goodies are viewable by the spider. If they are not viewable, they will not be spidered, not indexed, not processed, etc. - in a word they will be non-existent for search engines.

After a page is crawled, the next step is to index its content. The indexed page is stored in a giant database, from where it can later be retrieved. Essentially, the process of indexing is identifying the words and expressions that best describe the page and assigning the page to particular keywords. For a human it will not be possible to process such amounts of information but generally search engines deal just fine with this task. Sometimes they might not get the meaning of a page right but if you help them by optimizing it, it will be easier for them to classify your pages correctly and for you – to get higher rankings.
When a search request comes, the search engine processes it – i.e. it compares the search string in the search request with the indexed pages in the database. Since it is likely that more than one page (practically it is millions of pages) contains the search string, the search engine startscalculating the relevancy of each of the pages in its index with the search string.
There are various algorithms to calculate relevancy. Each of these algorithms has different relative weights for common factors like keyword density, links, or metatags. That is why different search engines give different search results pages for the same search string. What is more, it is a known fact that all major search engines, like Yahoo!, Google, Bing, etc. periodically change their algorithms and if you want to keep at the top, you also need to adapt your pages to the latest changes. This is one reason (the other is your competitors) to devote permanent efforts to SEO, if you'd like to be at the top.
The last step in search engines' activity is retrieving the results. Basically, it is nothing more than simply displaying them in the browser – i.e. the endless pages of search results that are sorted from the most relevant to the least relevant sites.

2. Differences Between the Major Search Engines


Although the basic principle of operation of all search engines is the same, the minor differences between them lead to major changes in results relevancy. For different search engines different factors are important. There were times, when SEO experts joked that the algorithms of Bing are intentionally made just the opposite of those of Google. While this might have a grain of truth, it is a matter a fact that the major search engines like different stuff and if you plan to conquer more than one of them, you need to optimize carefully.
There are many examples of the differences between search engines. For instance, for Yahoo! and Bing, on-page keyword factors are of primary importance, while for Google links are very, very important. Also, for Google sites are like wine – the older, the better, while Yahoo! generally has no expressed preference towards sites and domains with tradition (i.e. older ones). Thus you might need more time till your site gets mature to be admitted to the top in Google, than in Yahoo!.


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